An automobile has an engine and a battery, wherein the battery is charged with power of the engine. A known technique of charge control for charging the battery suppresses the battery from being charged during normal running to save the amount of fuel consumption, while allowing the battery to be charged by regenerative power generation during deceleration running.
Idle reduction control is also known as the technology to save the amount of fuel consumption. Patent Literature 1 given below discloses an automobile having both the function of charge control and the function of idle reduction control, in order to meet the requirement for improvement of fuel consumption.
In the above prior art, however, when the amount of electric power accumulated in the battery is consumed by auxiliary machinery during an engine stop by idle reduction control, the engine may be restarted due to shortage of SOC (state of charge). Herein “SOC” is an index indicating how much electric power remains in the battery. Especially in the above prior art, since there is only a little surplus of SOC by the function of charge control, the engine is likely to be restarted due to shortage of SOC. This does not sufficiently improve the fuel consumption, and there is still room for further improvement.